Question: The price of a visit to the dentist is calculated according to the formula $50+100n$ where $n$ is the number of cavities the dentist finds. On your last visit to the dentist, $2$ cavities were found. What was the cost of your visit? $\$$
Answer: Having ${2}$ cavities tells us that $n={2}$. Let's substitute $n={2}$ into the expression and evaluate: $\begin{aligned} &\phantom{=}50+100n\\\\ &= 50 + 100\left({2}\right)\\\\ &= 50+200\\\\ &={250} \end{aligned}$ The cost of the visit to the dentist will be $\${250}$ if the dentist finds $2$ cavities.